U.S. patent application number 15/123541 was filed with the patent office on 2017-03-23 for tire building drum for the manufacture of tires.
This patent application is currently assigned to COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN. The applicant listed for this patent is COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN, MICHELIN RECHERCHE ET TECHNIQUE, S.A.. Invention is credited to Gerard BOR.
Application Number | 20170080657 15/123541 |
Document ID | / |
Family ID | 50473688 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170080657 |
Kind Code |
A1 |
BOR; Gerard |
March 23, 2017 |
TIRE BUILDING DRUM FOR THE MANUFACTURE OF TIRES
Abstract
The building drum includes a support (20), a central shaft (30)
and an outer circumferential surface coaxial with the axis of
rotation of the drum. The building drum also has a principal
cylindrical surface (100) axially bounded by a shoulder (101)
extended by a lateral protuberance (102) for receiving the products
which have to be assembled. Several segments together define the
principal cylindrical surface, and those segments are being divided
into first and second groups of adjacent segments (103a, 103b)
mounted so as to move between a first position in which they are
circumferentially juxtaposed and a second position in which the
adjacent segments are radially offset. Several adjacent elbow
levers (140) form the shoulder (101) and the protuberance (102) in
the expanded position of the drum and each elbow lever (140) is
mounted with articulation on the segment (103a, 103b) and on the
support (20).
Inventors: |
BOR; Gerard; (Ladoux,
Clermont-Ferrand Cedex 9, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN
MICHELIN RECHERCHE ET TECHNIQUE, S.A. |
Clermont-Ferrand
Granges-Paccot |
|
FR
CH |
|
|
Assignee: |
COMPAGNIE GENERALE DES
ETABLISSEMENTS MICHELIN
Clermont-Ferrand
FR
MICHELIN RECHERCHE ET TECHNIQUE, S.A.
Granges-Paccot
CH
|
Family ID: |
50473688 |
Appl. No.: |
15/123541 |
Filed: |
March 5, 2015 |
PCT Filed: |
March 5, 2015 |
PCT NO: |
PCT/EP2015/054656 |
371 Date: |
September 2, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29D 30/248 20130101;
B29D 30/244 20130101; B29D 30/247 20130101 |
International
Class: |
B29D 30/24 20060101
B29D030/24 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 7, 2014 |
FR |
1451866 |
Claims
1. A building drum (10) for building a tire, comprising; a support
(20), a central shaft (30) and an outer circumferential surface
coaxial with the axis of rotation of the drum and comprising a
principal cylindrical surface (100) axially delimited on both sides
by a shoulder (101) extended by a lateral protuberance (102) for
receiving the products to be assembled, several segments together
defining the principal cylindrical surface, said segments being
divided into first and second groups of adjacent segments (103a,
103b) mounted to move between a first position in which they are
circumferentially juxtaposed and a second position in which
adjacent segments are radially offset, and wherein several adjacent
elbow levers (140) form the shoulder (101) and the protuberance
(102) in the expanded position of the drum and wherein each elbow
lever (140) is mounted with articulation on the segment (103a,
103b) and on the support (20).
2. A building drum as set forth in claim 1, further including a
positive activator for pivoting each elbow lever (140) about an
axis perpendicular to the axis (X-X') of the drum.
3. A building drum as set forth in claim 1, wherein the segments
(103a, 103b) comprise end parts (103a', 103b') which can be moved
axially and radially between a first position in which the
principal cylindrical surface of the segments has a diameter and
axial length which are greater than those of a second position.
4. A building drum as set forth in claim 3, wherein the segments
(103a, 103b) comprise central parts (103a'', 103b'') supported
through radial arms (50) by a central collar (40) mounted on the
central shaft (30) of the drum and wherein said end parts (103a',
103b') are mounted so as to slide in relation to the central
parts.
5. A building drum as set forth in claim 1, wherein said elbow
lever (140) is a one-piece rigid part having the general shape of a
Z.
6. A building drum as set forth in claim 5, wherein the elbow
levers (140) can move by pivoting about an axis perpendicular to
the longitudinal axis (X-X') of the drum when driven by a collar
(160, 150) which can move in translation on the central shaft
(30).
7. A building drum as set forth in claim 6, wherein each collar
(160, 150) is connected to a group of segments (103a, 103b) and
wherein collars (160, 150) are mounted at a distance from each
other on the central shaft (30).
8. A building drum as set forth in claim 7, further including a
collar activator for activating the collars (160, 150) to move
together and apart symmetrically in relation to each other.
9. A building drum as set forth in claim 8, wherein said collar
activator includes a stop plate (190) of one piece with the collar
(160) and mounted with predetermined axial play in relation to the
collar (150).
10. A building drum as set forth in claim 1, wherein the elbow
lever (140) comprises a substantially radial arm (141) having a
height that is 50 mm or more in the expanded position.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention claims priority to PCT International
Patent Application Serial No. PCT/EP2015/054656 filed Mar. 5, 2015
entitled "Tyre Building Drum For The Manufacture Of Tyres," which
claims the benefit of FR Patent Application Serial No. 1451866
filed Mar. 7, 2014, the entire disclosures of the applications
being considered part of the disclosure of this application and
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This disclosure relates to a building drum for the
manufacture of tires.
[0004] The disclosure relates more particularly to a building drum
having shoulders on which the bead wire or bead wires are deposited
in the course of assembly through a lateral approach towards the
said shoulders. Through such a drum, different rubber-based plies,
including a carcass ply, can be placed in succession on the outer
receiving cylindrical surface and bead wires and semi-finished
products or profiled elements based on a rubber mixture can be
positioned on the shoulders located in the vicinity of the axial
extremities of the receiving surface and held there assembled,
together with the rubber-based plies previously positioned and
folded back at the shoulders. The bead wires and the semi-finished
products are held against the shoulder by adhesively bonding the
products together.
[0005] Because the carcass formed upon it shrinks from the drum,
the circumference of the drum has to be reduced to release the
carcass and ensure that there is release between the outer
circumference of the drum and the inner circumference of the
carcass. The drum must therefore be radially retractable so that
the green tire so assembled can be withdrawn. Such a drum generally
comprises a plurality of segments which can move radially between a
deployed or working position of the drum and a retracted position.
In addition to this, some tire carcasses have inclined shoulders
which also make it necessary for segments to be withdrawn
axially.
[0006] 2. Related Art
[0007] Thus publication WO 02/053355 in the name of the applicants
describes such an expandable building drum with inclined shoulders.
The building drum comprises a body mounted to rotate on a central
shaft, comprising a cylindrical assembly surface formed of several
shoulder segments. The segments are circumferentially adjacent,
they are provided with covering plates to ensure an outer surface
of circular shape, and are mounted so that they can move radially
and axially between an expanded position of the drum and a
retracted position of the drum. One disadvantage of this drum is
the use of vacuum valves connected to a pneumatic circuit with a
view to ensuring that the components are held at the shoulders,
which requires an additional feed source, complicates construction
of the drum and renders operation less reliable. Another
disadvantage of such a drum relates to activation of the segments,
which is brought about through a connecting rod that follows the
profile of a cam in the deployed position, return to the retracted
position being brought about by a resilient membrane enveloping the
segments, which gives rise to concerns about reliability as the
membrane wears or ages. In addition to this, the drum comprises
many segments, which increase in number with the difference in
diameter between the working and retracted positions of the drum.
Because of this, this drum is not suitable for building small
diameter carcasses, or those having a significant difference
between the diameter of the outer cylindrical surface and the
diameter measured at the beads thereof.
[0008] One solution has been described in document FR 2 509 663 in
which the drum comprises two different groups of segments, of the
keystone and voussoir type, arranged successively in a
circumferential direction. The segments are mounted so as to move
between a deployed position of the drum, in which all the segments
are circumferentially adjacent, and a retracted position of the
drum in which the segments are radially offset and retracted. Each
segment is connected by articulated arms, activating a central
slide which can move axially, two coaxial slides being provided
within the drum, one connected to the keystone segments and the
other to the voussoir segments. The drum also comprises means for
moving the slides.
[0009] The shoulders are connected to the arms activating the
segments via a mechanism with a rack and toothed sector, a
mechanism which ensures that they move axially in relation to the
segments and at the same time, so that the green tire built on the
drum can be removed. Adjustment of all the racks to achieve
segments which are concentric and parallel to the axis of the drum
proves to be difficult.
[0010] In a variant the drum comprises shoulders mounted so as to
be articulated on the segments. Each shoulder is mounted using a
tie rod, which is articulated on an articulated element mounted
with a tension spring in relation to the segment. The articulated
element is activated by means of a toothed sector on an activating
arm of a segment which engages an articulated cam and which pushes
the shoulder tie rod outwards in the deployed position of the drum.
Such a tensile spring solution gives rise to reliability problems
if the spring should jam or break.
[0011] As the shoulders are kinematically connected to the
segments, radial movement of the segments simultaneously brings
about movement of the shoulders, either in an axially sliding
direction or pivoting about an axis perpendicular to the axis of
the drum, to release the shoulders with respect to the parts
forming the bead of the green tire.
[0012] However the mechanism activating the segments and shoulders
of the drum according to this document is complex and bulky, which
has consequences for the dimensions, reliability and cost of the
drum. In addition to this, because of the large number of
articulated parts of which the drum is made up, significant chatter
and operating play have to be taken into account, play which
becomes greater as the mechanisms wear.
SUMMARY OF THE INVENTION AND ADVANTAGES
[0013] The disclosure is intended to overcome all of these
disadvantages.
[0014] Over and above, there is still a need for a retractable
building drum with shoulders of sufficient height to allow a green
tire whose beads are made only by a lateral approach, without
movement of the rubber at the shoulder of the drum, to be
built.
[0015] This objective is accomplished through the disclosure which
provides an building drum for the building of a tire comprising a
support, a central shaft and an outer circumferential surface
coaxial with the axis of rotation of the drum, and comprises a
principal cylindrical surface axially bounded by a shoulder,
extended by a lateral protuberance receiving the products being
assembled, several segments together defining the principal
cylindrical surface, the segments being divided into first and
second groups of adjacent segments mounted to move between a first
position in which they are circumferentially juxtaposed and a
second position in which the adjacent segments are radially offset,
and wherein, in the expanded position of the drum, several adjacent
elbow levers form the shoulder and the protuberance, and in that
each elbow lever is mounted with articulation on the segment and on
the support.
[0016] Such an elbow lever comprises at least two rigid arms
forming a given angle between them. The elbow lever comprises a
shape which, by revolution about the axis of the drum, defines the
surface of the shoulder and that of the lateral protuberance of the
building drum, surfaces which are coaxial with the outer
cylindrical surface and the axis of rotation of the drum. Such an
elbow lever is sufficiently rigid to be able to take up the
stitching forces applied to the shoulders during assembly without
deformation, so that the components adhere together.
[0017] Articulated mounting of the elbow lever on the edge of each
segment and on the support allows the lateral part of the drum to
tilt through a large amplitude when the lever is caused to pivot
about the support during radial retraction of the segments and to
return to its retracted position, doing so in a reliable operating
manner. This means that the shoulder of the drum can be of great
height, while limiting play and chatter in the articulations. Also,
this tilting of the elbow lever makes it possible to remove the
carcass without stressing the assembled components or causing them
to slide between each other.
[0018] Such a drum makes it possible to construct the bead zone
with only lateral approach of the components onto the drum, without
stressing these components (that is without folding or deforming
one of the components at the shoulder) when assembling the carcass
on the drum, while preventing the components from sliding between
themselves when the carcass is extracted. The bead zone of the
carcass or green tire so obtained is close to its final shape.
[0019] Preferably the drum according to the disclosure comprises
means positively activating pivoting of each elbow lever about an
axis perpendicular to the axis of the drum.
[0020] By positive pivoting activating means are meant means
comprising a moving mechanical member which causes the elbow lever
to pivot through direct contact or through the intermediary of
rigid elements when the segments move towards the expanded or
retracted position of the drum. Such positive activation makes it
possible to ensure that the lever will pivot reliably, so that the
articulation connecting the elbow lever to the extremity of the
segment can pass from a first position in which it is located in
the vicinity of the outer cylindrical surface of the segment and
overlies the second articulation connecting the lever to the
support, to a second position in which it descends at least
substantially to the same level as the second one.
[0021] According to one advantageous aspect of the disclosure, the
segments comprise extremity parts which can move axially and
radially between a first position in which the principal
cylindrical surface of the segments has a diameter and axial length
greater than those in a second position.
[0022] Preferably the segments comprise central parts supported by
means of radial arms by a central collar mounted on the central
shaft of the drum and the extremity parts are mounted so as to
slide in relation to the central parts.
[0023] According to the disclosure the elbow lever is a one-piece
rigid part having a general Z shape. Such a lever comprises three
arms, the first and the second defining the surfaces of the
shoulder and the lateral protuberance, whereas the third is used
for pivoting activation.
[0024] Advantageously the elbow levers can move by pivoting about
an axis perpendicular to the longitudinal axis of the drum when
driven by a collar which can move in translation along the central
shaft. Axial movement of a collar parallel to the longitudinal axis
of the drum engaging one of the extremities of each lever directly
brings about pivoting movement of the elbow lever about a pivot
axis of the support which is perpendicular to the longitudinal axis
of the drum.
[0025] According to one advantageous aspect of the disclosure, each
collar is connected to a group of segments and the collars are
mounted at a distance from each other on the central shaft. This
makes it possible for each group of segments to be activated
independently.
[0026] Preferably the drum according to the disclosure comprises
activating means which move the collars towards or away from each
other symmetrically.
[0027] According to one advantageous aspect of the disclosure the
activating means comprise a stop plate of one piece with the collar
and mounted with predetermined axial play in relation to the
collar. This makes it possible to activate and move a first group
of segments.
[0028] According to the disclosure, the elbow lever comprises a
substantially radial arm in an expanded position, having a height
of 50 mm or more. The height of the radial arm of the elbow lever
defines the height of the shoulder of the drum. A drum having a
shoulder of height over 50 mm can be used to build the bead zone of
a green tire having dimensions larger than 16'' only through
lateral approach of the components on the drum, without stressing
these components (that is without folding or deforming one of the
components) when assembling the carcass on the drum, while
preventing the components from sliding between themselves when the
carcass is extracted.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The disclosure will be better understood through the
description below, which is based on the following figures:
[0030] FIG. 1a is a view in axial cross section of the building
drum according to the disclosure with only two adjacent segments
illustrated in the expanded position;
[0031] FIG. 1b is a view in axial cross section of the building
drum according to the disclosure with only two adjacent segments
illustrated in the retracted position;
[0032] FIG. 2a is a front view and FIG. 2b is a view in transverse
cross section of a drum according to the disclosure in the expanded
position;
[0033] FIG. 3a is a front view and FIG. 3b is a view in transverse
cross section of a drum according to the disclosure in the
retracted position;
[0034] FIG. 4 is a kinematic diagram of the drum showing a segment
of the first group of segments of the drum in the expanded
position;
[0035] FIG. 5 is a kinematic diagram of the drum showing a segment
of the second group of segments of the drum in the expanded
position;
[0036] FIG. 6 is a kinematic diagram of the drum illustrating the
segment in FIG. 4 in the retracted position; and
[0037] FIG. 7 is a kinematic diagram of the drum illustrating the
segment in FIG. 5 in the retracted position.
DETAILED DESCRIPTION OF THE ENABLING EMBODIMENT
[0038] In the various figures identical or similar elements have
the same reference number. Their descriptions are not therefore
systematically repeated.
[0039] FIGS. 1a and 1b show a building drum 10, comprising a
support 20 of one piece with a central shaft 30. Central shaft 30
is driven in rotation together with support 20 about a longitudinal
axis X-X' of the drum. Building drum 10 has an outer
circumferential surface comprising a principal cylindrical surface
100 for receiving the products which have to be assembled, axially
bounded by a shoulder 101 which is extended axially at its base by
lateral protuberance 102. Principal cylindrical surface 100
comprises segments which are circumferentially juxtaposed in the
expanded or working position of the drum and mounted so as to move
radially and axially in relation to support 20 mounted on shaft 30.
The segments allow drum 10 to be radially retracted so that
carcasses built on the drum can be removed.
[0040] The segments comprise a set of several segments of a first
and second group of alternating and circumferentially adjacent
segments. Thus the circumferentially lateral surfaces of segments
103a of a first group of segments are convergent on the outside of
the drum, these segments being called keystone segments and the
circumferentially lateral surfaces of segments 103b of a second
group are convergent within the drum, these segments being called
voussoir segments. When they are activated the keystone segments
are displaced radially inwards before the voussoir segments,
between an expanded or working position of the drum which may be
seen in FIGS. 2a and 2b, when the lateral surfaces of two adjacent
segments are in contact, and a retracted position thereof which may
be seen in FIGS. 3a and 3b, the diameter of the envelope comprising
the outer surfaces of segments 103a being smaller than that of the
envelope comprising the outer surfaces of segments 103b in the
retracted or folded position of drum 10.
[0041] Drum 10 has a lateral protuberance 102 which is of one piece
with shoulder 101, and has a generally cylindrical bearing surface
of diameter less than that of principal cylindrical surface 100, so
that shoulder 101 is released to allow bead wires and other
semi-finished products intended to construct the bead zone to be
fitted through a lateral approach.
[0042] According to the disclosure, several adjacent elbow levers
140 form shoulder 101 and lateral protuberance 102 of drum 10.
Elbow lever 140 is a rigid piece which is mounted with articulation
on the edge of a segment 103a, 103b and on support 20 of the drum.
The lever thus comprises a first arm 141 which is substantially
radial in the expanded position of the drum, extended laterally by
a second arm 142. Arm 142 comprises a raised surface forming seat
144 located close to the junction with radial arm 141 and having a
slope to assist the introduction of components. Seat 144 can
receive and support the components of the green tire with a view to
stitching. The envelope surface passing through first arms 141
forms shoulder 101 and that passing through arms 142, more
particularly seats 144, forms lateral protuberance 102 of building
drum 10. The angle formed between arms 141 and 142 of lever 140 may
be a right angle, an acute or obtuse angle, and varies between
80.degree. and 100.degree.. When the shoulder is inclined outwards
in relation to radial direction (or forms an acute angle with the
lateral protuberance) the bead zone of the carcass obtained has a
shape close to the final shape of the tire, and movements of the
components are very limited, even non-existent. When the shoulder
is inclined inward (forming an obtuse angle with the radial
protuberance) the shape of the green tire is more suitable for
pressing.
[0043] In the embodiment illustrated in the figures, support 20 is
made in the form of an end flange attached to arm 30, two end
flanges laterally bounding the internal volume of drum 10. U-shaped
bridles 21 uniformly distributed over the circumference of the
flanges serve as the support for the articulations for levers 140.
Advantageously elbow lever 140 is a rigid part having a general Z
shape with three arms, 141, 142, 143 mounted to pivot about three
articulations 110, 120, 130 having axes perpendicular to
longitudinal axis X-X' of the drum. Lever 140 has a first arm 141
forming a shoulder, a second arm 142 forming a lateral protuberance
and a third arm 143 activating the pivoting movement. First
articulation 110 connects lever 140 to a segment 103a, 103b,
respectively, the second articulation 120 connects it to support
20, and third segment 130 connects it to a lateral collar 150, 160,
which is coaxial with shaft 30 of drum 10. At each extremity of
drum 10, two lateral collars 150, 160 are mounted to rotate with
support 20 and with the possibility of longitudinal movement
parallel to the X-X' axis of the drum. More particularly, collars
150, 160 are caused to move in translation in opposite directions
through a screw and nut assembly 170, as will be explained
below.
[0044] Each segment 103a, 103b is made in three parts: two end
parts 103a', 103b' which are identical and symmetrical in relation
to a median vertical plane and a central part 103a'', 103b''. The
end parts of the segments are connected by elbow levers 140 to
support 20, and the central parts of the segments are connected by
radial arms 50 to a central collar 40 attached to shaft 30. The end
parts of each segment are mounted so as to slide in translation on
two longitudinal rods 60 which are fixedly mounted on the central
part of the segment and extend on either side of the latter.
Longitudinal rods 60 serve to hold and guide the end parts in
relation to the central part of the segments. This assembly
prevents tilting of the end parts of the segments and guides them
parallel to central axis X-X' of drum 10 when the segments are
moved between the two extreme positions of the drum. The central
part of each segment supports a tile 70, which is fixedly mounted
on the outer surface thereof and is of a length such as to ensure
that it covers the gaps formed between the different parts of the
segment when the latter moves between the two extreme positions of
drum 10.
[0045] The kinematics of the drum and segments 103a, 103b will be
explained with reference to FIGS. 4 to 6. The drum is driven in
rotation about its central axis X-X' by a motor M1 which is coupled
to shaft 30. A motor M2 is coupled to a transmission shaft 180
which causes a screw 171 to rotate via a set of gears 181. Screw
171 comprises two threaded ends, a first 172 having a left hand
thread, and a second 173 having a right hand thread. Each threaded
extremity acts together with a nut 174, 175 each attached to a
collar 160 to allow collars 160 to move together or apart
symmetrically according the rotation of screw 171.
[0046] In what follows a single axial moiety, in particular the
equipment located on the left in FIGS. 4 to 6, will be described in
order to explain the concept of the disclosure, the segments being
symmetrically mounted with respect to a vertical median plane
containing the longitudinal axis of radial arms 50.
[0047] FIG. 4 shows a keystone segment 103a in the expanded
position of drum 10 and FIG. 6 the segment in the retracted
position of the drum. End part 103a' of the keystone segment has
the shape of a sector of a cylindrical shell having a thickness of
a few mm to a few cm, the outer lateral edge of which is rounded
and supports the axis of an articulation 110, about which is
pivotally mounted elbow lever 140. Lever 140 is mounted to pivot on
support 20 about an articulation 120 and it is also mounted with
the possibility of pivoting about an articulation 130 in relation
to collar 160. More particularly, collar 160 is in the shape of a
disc whose periphery is provided with radial arms comprising
bridles 161 (FIG. 1) for the attachment of linking bars 162, each
bar being attached to collar 160 through a shaft 163. The pivot
axis of articulation 130 lies at the end of linking bar 162
opposite that of the attachment to collar 160, longitudinal
translational movement of collar 160 enabling lever 140 to pivot
about axis of articulation 120, oscillations of articulation 130
being taken up by linking bar 162. In a variant the radial arms of
collar 160 may be made of one piece with linking bars 162, in which
case their ends terminate in guide grooves for rollers mounted on
the ends of arms 143.
[0048] FIG. 5 illustrates a voussoir segment 103b in the expanded
position of drum 10 and FIG. 7 of the same segment in the retracted
position of the drum. The end part 103b' of the voussoir segment
has the shape of a sector of a cylindrical shell having a thickness
of a few mm, the outer lateral edge of which comprises at its
center an articulation axis 110, about which elbow lever 140 is
mounted with the ability to pivot. Lever 140 is mounted to pivot on
support 20 about an articulation 120 and it is also mounted with
the ability to pivot about an articulation 130 in relation to
collar 150. More particularly, collar 150 is in the general shape
of a disc with several radial arms, the extremity (FIG. 1) of each
arm forming a groove 151 for guiding a roller 152 mounted on the
end of arm 143. Groove 151 has a U-shaped axial cross section and a
width greater than that of roller 152. Groove 151 acts as a housing
for receiving and guiding roller 152 during axial movement of
collar 150.
[0049] Collars 150 and 160 are coaxial with the X-X' axis and are
mounted so that their respective radial arms alternate
circumferentially, one arm of one collar being angularly at an
equal distance from the arms of the other collar. Keystone segments
103a and voussoir segments 103b are equipped with identical levers
140. In the expanded position of the drum, when the keystone and
voussoir segments are circumferentially adjacent, as may be seen in
FIGS. 4 and 5, the pivot axes of articulations 130 of all segments
103a, 103b lie in a same vertical plane passing through the
longitudinal axis of the drum and are tangential to a common circle
having a center passing through the X-X' axis of drum 10 and lie in
the vertical plane.
[0050] Collars 150 and 160 are mounted so that they are able to
move in longitudinal translation when they are activated by a stop
plate 190 which is of one piece with the end of nut 174 of
screw-nut device 170. Collar 150 is mounted with play on three
rotation-preventing rods 191 parallel to the X-X' axis and
uniformly distributed about its circumference. Rods 191 have a top
stop 194 to limit the axial course of collar 150 in the expanded
position of the drum. A bottom stop 195 is mounted as one piece
with support 20 and limits the axial course of collar 160 in the
retracted position of the drum. Collars 150, 160 are axially offset
(that is in the direction of longitudinal axis X-X'), collar 160
occupying the position furthest from the center of drum 10. Stop
plate 190 and collar 160 are fixedly mounted to the lateral ends of
a bush 193. Collar 150 is mounted with the ability to slide on bush
193.
[0051] In the expanded position of drum 10 collars 150 and 160 are
held at a predetermined distance from each other by means of
compression springs 192, several springs 192 being distributed
circumferentially between the two collars. A functional play "j",
having a predetermined value, is provided between the front surface
of stop plate 190 and that facing collar 150, this play enabling
keystone segments 103a to be activated first.
[0052] In the embodiment illustrated in the figures, arm 141 of
elbow lever 140 has a height of 50 mm, which is appropriate for the
building of a 16'' tire. Levers having arms 141 of greater height
may be provided, adjusting the free volume within the drum to allow
greater axial movement of collars 150, 160 and greater tilting of
lever 140 so that articulation 110 can reach a position
substantially lower than the diameter of articulation 120.
[0053] The drum illustrated in the figures comprises nine keystone
segments 103a and nine voussoir segments 103b. The movement of
segments 103a, 103b between the expanded and retracted positions of
the drum is determined by the axial course of collars 150 and 160.
Movement of the segments can be altered by adjusting top stop 194
and bottom stop 195.
[0054] In operation, motor M2 is first commanded to bring all the
segments into the expanded position. In this position a carcass is
built by stitching different rubber-based plies onto building drum
10 which is caused to rotate by motor M1. The bead wires and other
rubber-based profiled elements are positioned on shoulder 101
through a lateral approach and are supported at their base on
lateral protuberance 102. The lateral surfaces of levers 140 are
advantageously covered with plates 145 fixedly mounted thereupon so
as to constitute a substantially continuous laying surface on
shoulder 101, on which the layers of rubber can be supported during
stitching, so that they adhere to each other.
[0055] When building of the carcass is complete, motor M2 is
commanded to be activated in the opposite direction to collapse the
segments. Movement of screw-nut device 170 moves stop plate 190
pushing collar 160 in the direction of the lateral flange opposite
it, which, through the pivoting of levers 140 initiates inward
radial movement of keystone segments 103a. Thus only keystone
segments 103a are activated during travel of stop plate 190 through
the distance of play "j"; subsequently the latter simultaneously
pushes collars 150 and 160 with the result that set of keystone
segments 103a and voussoir segments 103b is moved radially towards
the interior of the drum. At the end of the travel of the axial
movement of stop plate 190 all the segments are radially retracted,
the keystone segments being in the position illustrated in FIG. 6,
the voussoir segments being in that illustrated in FIG. 7, the
whole of the drum being visible in FIGS. 3a and 3b. By causing
levers 140 to pivot, end parts 103a', 103b' of segments 103a, 103b
move radially inward and axially towards each other. At the same
time the shoulder moves inward and comes to lie completely below
the inner diameter of the bead zone, and the carcass can be removed
from building drum 10 and sent for finishing.
[0056] Other variants and embodiments of the disclosure may be
envisaged without going beyond the scope of the disclosure.
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